Scope troubles with a swap function
Matthew D. Wood
woodm at equire.com
Fri Aug 10 22:14:08 CEST 2001
Ok, so swap works, just like you said it should. (I'm still mad that I
didn't see that.)
however, the next project is to write a 'cycle_variables' function (or
single line like you did before.)
So, this time, we take an arbitrary number of variables, and cycle them
def cycle (*vars) :
print 'Cycling the variables...'
vars = list(vars)
temp = vars
for index in range(len(vars) - 1) :
vars[index] = vars[index + 1]
vars[-1] = temp
print 'See, I cycled them!'
A = 'a'
B = 'b'
C = 'c'
D = 'd'
print """Here's the original set:"""
print (A, B, C, D)
cycle(A, B, C, D)
print (A, B, C, D)
print """Oh, I guess I didn't really cycle them afterall."""
Obviously, that example doesn't work. Is there a way to make it work?
I don't necessarily know if such a function would be all that usefull,
but I can't sleep at night because I haven't been able to figure out the
solution. (That's a little exageration :'-( )
And once again, thanks for all you guys/gals who have helped me out.
Hans Nowak wrote:
>> ===== Original Message From "Matthew D. Wood" <woodm at equire.com> =====
>> Ok, I've been banging my head against this for a sufficiently long time
>> that I feel justified in presenting this personal challenge to the list.
>> How do you make a swap function?
> You don't need to. :) Use:
> a, b = b, a
>> How do you make a function or a callable object instance that will do
>> what the following code intends to do:
>> def swap (heaven, hell) :
>> purgatory = heaven
>> heaven = hell
>> hell = purgatory
> Python's internal workings are very different from languages like C and
> Pascal. A Python "variable" is not a location in memory that you can fill with
> arbitrary data. This Pascal code:
> X := 3;
> X := 42;
> changes the value of X, which resides at a certain location in memory. But the
> equivalent Python code
> x = 3
> x = 42
> does not do exactly the same; rather, it binds the name 'x' to the value 3,
> then rebinds that name to the value 42. Other people explain this better than
> me; see
> --Hans Nowak
-------------- next part --------------
An HTML attachment was scrubbed...
More information about the Python-list